Recently, as the possibility of the exhaustion of limited petroleum resources and environmental problems, such as air pollution caused by exhaust gas from vehicles, constitute serious social problems, the exploitation of environment-friendly alternative energy sources and research on new transportation means have actively progressed. Thus, several means, such as an electric vehicle or a hydrogen fueled car, have been proposed. In particular, interest in a “human powered vehicle”, which is used as a transportation means for a relatively short distance and obtains its propelling force from human power, has increased.
Currently, a representative transportation means driven by human power is a general bicycle, which is driven by a crank wheel system for two wheels. Such a bicycle permits free movement, but has very low driving stability because of structural characteristics. Further, only one person may ride the bicycle, so that it is difficult to actually use the bicycle as a systematic transportation means.
Another type of human powered vehicle has been proposed in U.S. Pat. No. 271,720, No. 1,013,041, etc, which disclose a railroad velocipede. The railroad velocipede is constructed so that wheels are rotated by the swinging movement of an actuating lever connected to the wheels via a link mechanism, and are driven along rails.
However, the railroad velocipede has a construction similar to that of a general bicycle. That is, a pair of main wheels, which are provided at front and rear positions, is mounted on one rail of the track, and one subsidiary wheel is mounted on the other rail of the track, thus supporting and guiding the body of the velocipede. Hence, the number of passengers is limited to one or two, and the stability is poor. Further, the actuating lever is operated with both hands, so that the action of the passengers is very restricted while driving, and thus the invention is not convenient.
For these reasons, the railroad velocipede is used only as a moving means in a special situation, for example, railroad repair work, but is not used as a public transportation means. Especially, since the railroad velocipede is directional, the railroad velocipede may be driven in only one direction (a forward direction). When one desires to reverse the direction (backwards direction), the body of the velocipede must be lifted and rotated to face the opposite direction, thus inconveniencing the passengers.
Meanwhile, recently, a new railroad velocipede has been proposed. The railroad velocipede is provided with four wheels, like an automobile. The wheels are stably mounted on both rails of a track. The railroad velocipede can be easily driven by the pedaling of a crank wheel system. The railroad velocipede has several seats, so that a relatively large number of passengers can ride the railroad velocipede.
However, the four-wheeled railroad velocipede moves in only one direction, so that it is impossible to reverse the direction thereof (conduct forward and backward movement). Thus, when a passenger desires to move the railroad velocipede backwards, the body of the velocipede must be raised and rotated. Further, when it is required to change a driver during the driving, the railroad velocipede must be stopped and passengers must exchange seats with each other. Thus, it is difficult to smoothly drive the railroad velocipede. For these reasons, when the railroad velocipede is driven without changing the driver, the physical strength of the driver may be excessively consumed, so that it is difficult to drive a long distance.
Further, a one-way clutch is a device which transmits power from a driving shaft to a driven shaft only in one direction in a power transmission device the driving shaft and driven shaft of which are driven in the same direction, like a chain drive or a belt drive. The one-way clutch has been widely used in various kinds of devices which do not require the conversion of the driving direction, for example, a bicycle and a motorcycle.
For example, U.S. Pat. No. 1,254,434 proposed a human powered vehicle which is driven on a railroad by a crank pedal system using a chain. The human powered vehicle may require backward movement. However, the conventional one-way clutch cannot change the power transmission direction. Thus, when it is required to move backward, the human powered vehicle must be pushed backwards or must be lifted in order to change its direction.
In order to apply a one-way clutch capable of changing direction to the human powered vehicle, a direction conversion means for changing the power transmission direction from the exterior must be also provided. In particular, if the direction conversion means is manipulated during the driving, the human powered vehicle may endanger the passengers, because of the structural characteristics of the human powered vehicle. Thus, for safety, the power transmission direction must be converted when the vehicle is completely stopped.